The Axial Nonlinear Vibration Analysis of Ball-screw about Machine Tool Feeding System

The forced state of the ball-screw of machine tool feeding system is analyzed. The ball-screw is simplified as Timoshenko beam and the differential equation of motion for the ball-screw is built. To obtain the axial vibration equation,the differential equation of motion is simplified using the assumed mode method. Axial vibration equation is in form of Duffing equation and has the characteristics of nonlinearity. The numerical simulation of Duffing equation is proceeded by MATLAB / Simulink. The effect of screw length,exciting force and damping coefficient are researched,and the axial vibration phase track diagram and Poincare section are obtained. The stability and period of the axial vibration are analyzed. The limit cycle of phase track diagram is enclosed. Axial vibration has two type-center singularity distributions on both sides of the origin. The singularity attracts vibration to reach a stable state,and Poincare section shows that axial vibration appears chaotic motion and quasi periodic motion or periodic motion. Singularity position changes with the vibration system parameters,while the distribution doesn’ t change. The period of the vibration is enhanced with increasing frequency and damping coefficient. Test of the feeding system ball-screw axial vibration exists chaos movement. This paper provides a certain theoretical basis for the dynamic characteristic analysis of machine feeding system ball-screw and optimization of structural parameters.

On Axially Symmetric Vibrations of Fluid Filled Poroelastic Spherical Shells

Employing Biot’s theory of wave propagation in liquid saturated porous media, waves propagating in a hollow poroelastic closed spherical shell filled with fluid are studied. The frequency equation of axially symmetric vibrations for a pervious and an impervious surface is obtained. Free vibrations of a closed spherical shell are studied as a particular case when the fluid is vanished. Frequency as a function of ratio of thickness to inner radius is computed in absence of dissipation for two types of poroelastic materials each for a pervious and an impervious surface. Results of previous works are obtained as a particular case of the present study.

Vibration Analysis of an Infinite Poroelastic Circular Cylindrical Shell Immersed in Fluid

The purpose of this paper is to study the effect of presence of fluid within and around a poroelastic circular cylindrical shell of infinite extent on axially symmetric vibrations. The frequency equation each for a pervious and an impervious surface is obtained employing Biot’s theory. Radial vibrations and axially symmetric shear vibrations are uncoupled when the wavenumber is vanished. The propagation of axially symmetric shear vibrations is independent of presence of fluid within and around the poroelastic cylindrical shell while the radial vibrations are affected by the presence of fluid. The frequencies of radial vibrations and axially symmetric shear vibrations are the cut-off frequencies for the coupled motion of axially symmetric vibrations. The non-dimensional phase velocity as a function of ratio of thickness to wavelength is computed and presented graphically for two different types of poroelastic materials for thin poroelastic shell, thick poroelastic shell and poroelastic solid cylinder.

Integral sliding mode control for flexible ball screw drives with matched and mismatched uncertainties and disturbances

The design of servo controllers for flexible ball screw drives with matched and mismatched disturbances and uncertainties is focused to improve the tracking performance and bandwidth of ball screw drives.A two degrees of freedom mass model is established based on the axial vibration characteristics of the transport ball screw,and the controller of an adaptive integral sliding mode is proposed combining the optimal design of state feedback gain matrix K to restrain the vibration and the matched disturbances and uncertainties.Then for the counteraction of the mismatched disturbances and uncertainties,a nonlinear disturbance observer is also developed.The trajectory tracking performance experiments and bandwidth analysis were conducted on experimental setup with the proposed control method.It is proved that the adaptive integral sliding mode controller has a high tracking performance and bandwidth especially for the axial vibration characteristics model of ball screw drives.And the ball screw tracking accuracy also has a considerable improvement with the application of the proposed nonlinear disturbance observer.

精密滚珠丝杠副轴向振动激励因素的试验研究

由于精密滚珠丝杠副的轴向振动是影响定位精度和噪声的重要因素,对多根型号为4020×1200的滚珠丝杠进行了在不同速度下的轴向振动试验。试验结果表明,滚珠丝杠副的轴向振动由一个随转速而变化的周期性激励因素引起,为确定此激励源,分析了不同激励因素。分析结果表明,滚珠进入返向器时的冲击是滚珠丝杠副轴向振动的主要激励因素。

进给驱动机构轴向振动与滚珠丝杠滚振研究

考虑扭转和轴向振动的滚珠丝杠副进给驱动机构建立动力学模型,对其固有动力学特性进行数值计算,提出进给驱动系统复杂振动中滚振的概念。利用MATLAB和ADAMS软件建立滚珠丝杠副进给驱动系统机电联合仿真平台,利用高分辨率旋转编码器和直线光栅尺等建立其动力学特性实验平台,对系统轴向和扭转动力学特性进行仿真分析与实验测量。实验结果表明:进给驱动机构第一阶模态在移动部件轴向振动的同时还存在滚珠丝杠的滚振,此滚振虽不会引起丝杠的扭转变形,但因其包含在伺服控制环之内,且频率较低、能量较大,会严重限制伺服控制带宽并影响其稳定性,在高性能进给驱动系统的设计中必须对此加以重视。

机床进给系统滚珠丝杠轴向非线性振动分析

将机床进给系统滚珠丝杠简化为Timoshenko梁,对滚珠丝杠进行受力分析,建立滚珠丝杠的运动微分方程。采用假设模态法,对运动微分方程进行化简,得到丝杠轴向振动方程,轴向振动方程满足Duffing方程形式,轴向振动具有非线性特征。利用MATLAB对Duffing方程进行数值仿真,研究丝杠长度、激振力和阻尼系数对振动的影响,得到轴向振动的相轨迹图和截面,分析轴向振动的稳定性和周期性。相图极限环封闭,轴向振动具有两个中心型奇点分布在原点两侧,奇点对振动具有吸引作用,使系统轴向振动在奇点附近达到稳定状态,Poincare截面显示轴向振动出现混沌运动、拟周期运动或周期运动,奇点位置随振动系统参数变化,但分布情况不变化。周期性随着激振频率和阻尼系数的增大而增强。试验验证了机床滚珠丝杠进给系统轴向振动存在混沌运动。为滚珠丝杠进给系统的动态特性分析和结构参数优化提供了一定的理论基础。

螺杆轴向振动对熔体注射过程能耗的影响

研究了螺杆轴向振动对熔体注射过程中各个阶段能耗的影响,建立了振动力场作用下熔体流经圆锥形浇口流道和圆盘充模的物理模型和数学模型,并求得上述两个过程中功耗的解析式;通过实验验证了振动力场的引入使得注射过程能耗减小,在振动强度系数达到0．45以后,注射过程功耗减小的趋势更明显。

电磁动态塑化挤出机螺杆振动系统聚合物阻尼分析

对聚合物电磁动态塑化挤出机螺杆轴向振动系统,根据牛顿型粘性流体的剪切理论,确定了聚合物熔体的阻尼系统。为振动系统的求解以及实验测定提供了理论依据,同时为挤出机螺杆的机筒的优化设计奠定了基 础。

塑料动态注射成型机螺杆轴向脉动特性分析

采用液压激振力为驱动动力的运动机构方法,实现注射螺杆的轴向脉动,使熔融塑化、注射、保压过程均在周期性振动状态下进行。分析了此种振动装置在注射阶段脉动螺杆的动态响应以及振幅和频率的特性。通过研究表明,脉动注射时螺杆的振幅比振源的振幅有一定程度的减小,振动的平衡位置也发生了变化,但振动的频率不变。研究注射螺杆轴向脉动特性,对于设计脉动压力诱导注射成型机有一定的指导意义。

引入滚珠丝杠的齿轮式位移放大型振动控制装置工作机理与应用

在钢筋混凝土结构振动位移过小的情况下,为提升结构附加阻尼器的耗能减振作用,本文提出一种基于滚珠丝杠驱动,齿轮齿条啮合运动的新型位移放大型振动控制装置。文中对装置做了尺寸设计和运作机理分析,并对该装置进行了理论推导,得到了位移放大倍数、滚珠丝杠轴力理论公式、位移放大型阻尼器的阻尼力公式以及简谐作用下的滞回耗能公式。运用ABAQUS软件进行有限元分析,软件分析的伪静力数值试验结果与理论推导结果吻合完好,表明了以上推导公式的正确性。结合一个具体微振工程,在简谐激励作用下,对该大型回转装备-单层钢筋混凝土框架结构体系进行了数值模拟分析,结果表明使用该装置后结构的振动控制效果显著。

单螺杆振动塑化挤出机螺杆转动对其轴向振动的影响

建立了螺杆轴向振动的动力学模型,研究了模型的质量、阻尼、刚度和激励的简化计算方法,通过求解方程和分析,得出结论:当其他参数确定时,螺杆的转动能改变螺杆轴向振动的平衡位置,但不能影响其频率;转速恒定,螺杆轴向振动的振幅和初相角保持稳定;在一定范围内,转速越高(低),螺杆轴向振动的振幅越大(小)。

螺杆轴向振动对PVC／木粉复合材料挤出片材力学性能的影响

介绍了使用聚合物动态塑化单螺杆挤出机对聚氯乙烯(PVC)/木粉复合材料进行加工时,螺杆轴向振动对其挤出片材的拉伸性能的影响。将在振动频率为5～25 Hz、振幅为40～200μm下挤出的 PVC/木粉复合材料的拉伸性能和稳态状况下挤出的复合材料拉伸性能进行对比,从中找出最佳的振动参数范围。结果表明,振动频率为20 Hz、振幅为120μ m 时,复合材料的整体拉伸性能最佳,其拉伸强度、拉伸弹性模量、断裂伸长率和稳态相比都有较大的提高。

液压脉振注射成型过程的能耗分析

为降低液压脉振注射成型过程的总体能耗,文中对成型过程中螺杆轴向振动对熔体注射充模各阶段能耗的影响进行了研究,建立了振动力场作用下熔体流经圆管形流道的数学模型,推导出了相应的能耗表达式;并讨论了螺杆轴向振动振幅对注射成型总体能耗的影响.理论分析和实验结果表明:振动力场的引入使得注射过程总体能耗减小;螺杆轴向振动振幅在一定范围内变化时,能耗随振幅的增加而减小,振幅存在一个使得能耗最小的最佳值.

基于神经网络的液压脉振注射过程能耗分析

研究液压脉振注射成型过程中螺杆轴向振动对熔体注射充模各阶段能耗的影响,建立了振动力场作用下熔体流经圆管形流道的数学模型,推导出相应的能耗表达式。将BP神经网络引入注射过程的能耗研究中,并就振幅对能耗的影响进行仿真分析,验证了振动力场的引入使得注射过程能耗减小,及振幅存在一个使能耗最小的最佳值。

电磁动态挤出机转动与轴向振动之间特性关系研究

简要介绍了电磁动态挤出机的基本特征,通过实际螺杆简化成广义螺杆建立了振动的力学模型。通过实验测定了转速与振幅频率之间的关系,并通过实验验证了理论分析的合理性,并得到结论:在一定范围内,转速越高(低)螺杆轴向振动振幅越大(小),当其他条件确定时,转速随振幅或频率的增大而减小,但降低的幅度不大。

多功能振荡旋冲螺杆钻具研制与应用

随着油气资源勘探开发力度不断加大,深井、大位移井、水平井不断增多,钻井提速提效的需求更加迫切,尤其中深部地层机械钻速低的问题越来越凸显。因此,为了解决中深部硬地层破岩效率低、定向效率低的难题,自主创新研制了多功能振荡旋冲螺杆钻具,集转速扭矩、冲击振动、脉冲射流三种功能于一体,配套开发了测试平台和多通道数据采集系统,形成了Φ127~Φ244mm四种规格的系列化工具。现场48口井试验表明,多功能振荡旋冲螺杆钻具性能可靠、耐高温、使用寿命长,具有缓解近钻头托压、提高近钻头破岩效率的功能,平均机械钻速提高35.6%。建议在中深部地层中替代螺杆钻具推广应用。

TC4钛合金超高周次轴向振动疲劳试验

应用基于压电超声疲劳试验技术开发的20kHz轴向振动疲劳试验系统,完成了室温下TC4钛合金超高周疲劳试验,获得了TC4合金在107~109周次范围内的轴向振动疲劳寿命曲线(S-N曲线);运用C.Paris推导公式预测了TC4合金材料的寿命,得到各应力水平下破坏率为50%、95%、99%的安全寿命。结果表明:在疲劳循环大于107周次时,试件仍会发生疲劳断裂,疲劳强度随循环次数的增加而下降,并不存在明显的疲劳极限。TC4合金的S-N曲线在107~109周次的范围内呈连续下降型。在轴向振动超高周疲劳试验中,试件的裂纹扩展寿命只占其在50%破坏率下疲劳安全寿命的一小部分,其疲劳寿命主要由试件的裂纹萌生寿命决定。